Pain is the most frequently reported symptom and it is a common clinical problem that confronts the clinician. Many millions of people in the United States suffer from pain that is chronically undertreated or inappropriately managed. The clinical usefulness of the analgesic properties of opioids has been recognized for centuries, and morphine and its derivatives have been widely used for analgesia for decades in a variety of clinical pain states.
Nalbuphine HCl (17-(cyclobutylmethyl)-4,5α-epoxymorphinan-3,6α,14-triol hydrochloride) is a synthetic opioid agonist-antagonist analgesic belonging to the phenanthrene class of opioids. Nalbuphine is related to the opioid antagonist, naloxone, and also to the opioid analgesic, oxymorphone. Nalbuphine HCl is marketed in the United States under the trade name Nubain® by Endo Pharmaceuticals and is primarily a kappa agonist/partial mu antagonist analgesic.
Although oral administration of nalbuphine has been studied (Lo, M W et al. The Disposition and Bioavailability of Intravenous and Oral Nalbuphine in Healthy Volunteers, J. Clin. Pharmacol. 27:866-87.3 (1987); Aitkenhead, A R et al. “The Pharmacokinetics of Oral and Intravenous Nalbuphine in Healthy Volunteers, Br. J. Clin. Pharmacol. 25:264-288 (1988); Jaillon P, et al. Pharmacokinetics of Naibuphine in infants, Young Healthy Volunteers, and Elderly Patients, Clin. Pharmacol. Ther. 46:226-233 (1989)), it has never received marketing approval. Currently, nalbuphine is marketed only as an injection (10 mg/ml in 10 ml multiple dose vials; 20 mg/ml in 10 ml multiple dose vials; 10 mg/ml in 1 ml ampules; 20 mg/ml in 1 ml ampules) for intramuscular, subcutaneous, and intravenous administration.
The dosing interval of nalbuphine injection is approximately every three to six hours. Although the half-life following oral administration of immediate release nalbuphine has been reported to be somewhat longer (approximately five to seven hours), the drug effect generally wears off toward the end of the therapeutic window.